Answer by
LeheckaG (1826)
The "safest" way is to:
Set-out ant-baits in sheltered-areas where you have seen ants & where children & pets can not get at the ant-baits.
Ant baits contain chemicals which usually interfere with the ants development and/or reproduction.
Alternatively,
you could spray ant-insecticide,
but you risk contaminating water and/or children/birds/fish/pets.